1. Field of the Invention
The present invention relates to an analog-digital converting circuit, and more specifically to an analog-digital converting circuit which uses an analog-digital converter of a low resolution but can attain a high resolution.
2. Description of Related Art
Hitherto, for attaining analog-digital conversion (called "A/D conversion" hereinafter) at a high resolution, an A/D converter having a high resolution has been required. FIG. 1 illustrates one typical A/D converting circuit, which includes an A/D converter 10 having an input terminal 12 connected to receive an analog signal and a clock input connected to receive a sample clock 14 from a sample clock generator 16. The A/D converter 10 generates at its output terminal 18 a digital signal in the format of parallel bits, for example 10 bits.
The A/D converter 10 operates to convert the analog signal inputted to the input terminal 12, into the digital signal, in synchronism with the sample clock 14 supplied from the sample clock generator 16. In this A/D conversion circuit, in order to obtain a A/D conversion having a high resolution, the A/D converter 10 has to have a resolution higher than a required resolution.
However, the A/D converter having a high resolution is expensive in cost and very large in required consuming current. Therefore, it has been difficult to incorporate a high resolution A/D conversion circuit, into instruments required to be a lower power consumption, for example, a handy camera integrally combined with a magnetic recording/reproducing device.